@Chris Trottier I'm 41; I lived through that era. And the current Apogee is headed by Scott Miller, who was the founder of the original Apogee which later became 3D Realms. 

It may not be as big as it once was, but it's still just as indie.

EDIT: This should clear up the confusion: https://www.apogeeent.com/devblog/apogee-history 

 @Chris Trottier But Apogee still exists! It's weird to call an entirely different company a "spiritual successor" when the original company is still here with the same people running it!

https://www.apogeeent.com 

 @Chris Trottier And Apogee is back as an indie developer and publisher! 

 @Chris Trottier Also, if you want to know of a great book about John Romero's life and how he got into making PC games, check out his memoir Doom Guy: A Life in First Person. It's just as interesting (if not more so) than the games he creates!